In wireless communication systems in which wireless devices have multiple antennas and use beamforming techniques, the device on at least one end (or both ends) of a wireless link computes beamforming weights that are used when sending a transmission. When one device on the link is mobile, it is useful to update the beamforming weights to account for changing conditions in the wireless channel between the two devices.
Channel sounding is a procedure whereby a first device learns information about the wireless channel with respect to a second device, so that the first device can update its beamforming weights appropriately for use when sending a transmission to the second device. Some wireless communication systems operate in accordance with a wireless communication standard, e.g., the IEEE 802.11 standard for wireless local area networks (WLANs). The IEEE 802.11 standard specifies what is called an “explicit” beamforming feedback sounding procedure in which an access point (AP) and a client device follow a particular exchange of signals to convey information to the AP about the wireless channel between the AP and the client device.